Clinical electrotherapy devices are used to implement many different types of human medical therapy protocols. Electrotherapy devices may be used to stimulate nerves in the human body to a large number of therapeutic ends. In addition, electrical impulses cause muscles to contract and may be used for various forms of exercise and pain management.
TENS and microcurrent electrotherapy stimulation have been used successfully for the symptomatic relief and management of chronic intractable pain for many years. In general, TENS or micro current electrical nerve stimulation controls pain of peripheral origin by providing a counter stimulation that interferes with the painful sensations. While the mechanism of action of TENS is not fully understood, there are several theories as to how TENS helps to relieve pain. At the simplest level, stimulating peripheral nerves produces pleasant sensations that assist in distracting the patient from the pain sensation. This distraction is far from trivial and is often advanced as a universal method of pain relief focusing on both the conscious level and subconscious level.
One theory argues that the relief from pain is at least partly based on the knowledge that nerve transmissions carried by large nerve fibers travel more quickly than nerve transmissions carried by small nerve fibers. Under this theory, the electrical stimulations to large nerve fibers created by the TENS unit travel to the brain more quickly, and are more powerful, than pain impulses carried by smaller nerve fibers. Thus, the electrical impulses arrive at the brain sooner than the pain nerve impulses and the sensation of the large nerves overrides and blocks out the sensations from the smaller pain nerves.
Melzack and Walls proposed a working hypothesis of how TENS interferes with pain in 1965. Melzack and Walls proposed that TENS generates an artificial abnormal noise on the nerves to enervate the skin that shares the same nerve roots with the pain fibers conducting the real pain impulses. When the spinal cord receives the barrage of signals from the same region of the body, a neurological circuit turns off and stops relaying the pain impulses to the brain.
Another theory as to the mechanism of action of TENS is based on the understanding that serotonin and other chemical neurotransmitters participate in the pain and the pain reduction process. Under this theory, the electrical nerve stimulation caused by the TENS unit encourages the production of endorphins which then modulate the pain response. Alternately, the electrical stimulations in some way interfere with the production of serotonin which is involved in the pain response.
As a result of the increased understanding and studies surrounding the use of TENS in eliminating or minimizing patient pain, many attempts have been made to more efficiently and effectively implement TENS units. Compliance monitoring, power management, safety and comfort maximization, simplified unit designs, and a myriad of other techniques and methods have been advanced and modified with this increased use of TENS in mind.
Patient compliance with treatment is a medical concern regardless of the form of treatment being applied. Compliance refers to whether the patient is following through with the treatment as prescribed, whether the patient may be avoiding the treatment all together, or whether the patient is in some way applying the treatment in a manner that is not in a form the doctor prescribed and desired. If patients are non-compliant, it becomes very difficult to determine the effectiveness of treatment, as patients are often unwilling to admit they are non-compliant. In addition, some forms of electrotherapy treatment may cause discomfort in which case the patient may have a motivation to avoid the treatment despite its therapeutic benefit. Even further, non-compliance concerns can limit the potential for this treatment technique since misuse will likely weaken the economic and therapeutic draw for health care providers and insurance companies.
As a result of this necessity to implement a level of compliance, some current electrotherapy devices include compliance monitoring protocols. Generally, conventional compliance monitoring protocols include some means of recording the length of time for which the electrotherapy device has been utilized in the period since the doctor has prescribed its use. Conventional compliance monitors only record when the unit is on or off during a given time period. This leaves open the possibility of erroneously monitoring non-compliant use, since the patient may turn on the unit while it is not being utilized for therapeutic use, or the unit may be improperly connected during the power-on period. With regard to improper connections of the unit to the patient, the unit can mistakenly acknowledge therapeutic use during a period of use having no beneficial therapeutic effects on the patient. This leads to great uncertainty as to the effectiveness of the prescribed therapy, whether the current level of treatment is appropriate, or if it is in need of adjustment or discontinuation. Since electrotherapy is generally applied in non-constant electrical pulses, compliance monitoring becomes even more difficult. In general, the present art makes it necessary to maintain voltage during the periods of time in which electrical pulses are not being applied to the patient.
In the past, some compliance monitors have utilized transformers as part of the compliance monitoring circuitry in order to maintain voltage between timing impulses. Due to the physical electrical characteristics of transformers, they are difficult to miniaturize. This contributes to bulkier electrotherapy units. The preferred mode for the application of electrotherapy treatment is one where the treatment can be applied for extended periods of time. This protocol is most easily applied with a unit that can be worn on the body. This allows the treatment to be applied over a long period of time while the patient is involved in normal daily activities. If a unit is to be worn on the body for an extended period of time, a smaller unit is much preferred.
As stated, power management is an important hurdle to overcome in providing effective TENS treatment. The use of portable units capable of attachment to the human body requires battery operation. To promote treatment efficacy and to lower treatment costs, it is necessary to keep the TENS unit circuitry properly powered throughout the duration of the treatment, and to ensure that the patient or health care professionals will not need to replace batteries frequently, or at inopportune times. Conventional techniques to address such power management concerns have left room for measurable improvement. For instance, one technique has been to monitor the voltage level at the battery and to initiate a resulting warning system, such as an LED flash or display panel notification, upon determination by the device that the power has reached a point somewhere below a desired threshold. This system is obviously flawed since it fails to in any way conserve power, or modify performance in an attempt to lengthen the usable life of the battery source, and the resulting treatment period.
Another technique has been to monitor battery power for TENS units by setting a predefined ideal power level, frequently monitoring the overall power level, and making adjustments to power usage once the overall power level of the battery source has reached a level below the ideal power level. While this method does accommodate for lower power, it does so too late, using a power conservation plan that may prove to diminish treatment efficacy. First, power conservation and management is not approached until power has reached a dangerously low level. Second, this critical period of low battery power is dealt with by reducing output power for the TENS unit, which can be obviously undesirable if it negatively effects the proper therapeutic functioning of the unit on the patient.
Conventional attempts at controlling the output signal of the TENS unit to patients following disruptions, defective operations, or operator misuse have also proven problematic as they often fail to properly protect the patient, and the unit itself, from resulting surges. This surge phenomena often occurs when a lead connecting the TENS probe to the patient is disconnected from the main unit and reconnected while the patient is using the device. The natural reaction of the user or patient is to simply reconnect the lead and resume treatment. However, reconnection of the lead can result in a significant jump in power output—from zero to the treatment level. This jump in output signal is virtually instantaneous. As a result, such a quick spike or disruption can damage the unit and, more importantly, cause discomfort to, or even injure, the patient.
One attempt at dealing with the potential harm brought about by these disruptions, has been to provide for monitoring circuitry and/or software within the TENS unit to quickly detect the occurrence of such a disruption. Once the disruption has been detected, the unit quickly ramps down the output signal to approximately zero. At this point of reset, some units will await power approval and adjustment by the user/patient before treatment and power output will be resumed at defined levels. Other prior art teaches immediately ramping up the output signal to pre-disruption levels. Each of these approaches, while an improvement, can be improved upon.
Conventional approaches are directed to accommodation and output signal modification only after a surge has been detected. As a result, the patient and the TENS unit experience at least a momentary spike in the output signal, i.e., a surge upon reconnect of a disengaged lead to the unit. While continuous power surging is not permitted, it is still possible that the patient will be subjected to a period of physical discomfort.
Consequently, there is a need for a TENS unit that substantially overcomes the deficiencies and problems innately present with conventional systems and methods for compliance monitoring, power management, and disruption recovery, and the like.